Articulated arm transfer device

ABSTRACT

An articulated arm transfer device employs a pair of upper arms each upper arm being rotatable at its shoulder end, and a pair of forearms each forearm being rotatable at its wrist end. The elbow ends of each pair are connected to each other by a link means. The shoulder ends are mounted on a support in such a manner that one upper arm is rotated by a drive means, and holding means for an object to be transferred is mounted on the wrist ends. The link means includes shafts upon which the elbow ends are mounted and at least two S-bands connecting the shafts in such a manner that rotation of one shaft in either direction causes rotation of the other shaft in the opposite direction. The elbow end of one upper arm is fixed to its shaft, while the elbow end of the other upper arm is rotatably mounted on its shaft. The elbow end of one forearm is rotatably mounted on the shaft to which the elbow end of an upper arm is fixed, and the elbow end of the other forearm is fixed to the shaft on which the elbow end of the other upper arm is rotatably mounted.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The apparatus of the present invention relates generally to materialtransfer devices. The material transferred might include, but not belimited to, semiconductor wafers, such as Silicon and Gallium Arsenide,semiconductor packaging substrates, such as High Density Interconnects,semiconductor manufacturing process imaging plates, such as masks orreticles, and large area display panels, such as Active Matrix LCDsubstrates.

2. Description of the Prior Art

The transfer of delicate silicon wafers or the like between a pluralityof work stations or locations in the manufacture of semiconductordevices presents unique handling problems. The silicon wafers are verydelicate and have highly polished surfaces. When the wafers are abruptlymoved, they tend to slide. This sliding action can cause the siliconwafers to abrade or alternatively can cause damage to their edges ifthey collide.

There are numerous devices described in the prior art for transferringsilicon wafers. For example:

U.S. Pat. No. 3,823,836 discloses an apparatus which includes a supplycarrier with a plurality of ledges to hold the silicon wafers and awithdrawal device having a vacuum chuck. The vacuum chuck is attached toan elevator which raises and lowers the chuck. A horizontal transfer armcoupled to the vacuum chuck is used to transfer the silicon wafer fromthe supply carrier to a desired work station.

U.S. Pat. No. 3,370,595 discloses a wafer transfer handling apparatushaving an indexable carrier for transferring wafers to and from workstations. Wafers enter and leave the wafer carrier on an air slide withthe aid of a wafer ejector acceptor arm having directional air jets. Thewafer ejector acceptor arm controls the driving of the wafers into orout of the carrier from or onto the air slide, which moves the wafers toor from a work station.

U.S. Pat. Nos. 4,062,463, 3,874,525 and 4,028,159 also disclose wafertransfer devices which include either pneumatic components or grippingdevices for handling the wafers.

U.S. Pat. Nos. 4,666,366 and 4,909,701 disclose wafer transfer handlingapparatus having an articulated arm assembly which extends and retractsin a "froglike" motion to transfer an object such as a wafer between aplurality of locations. Two articulated arms are operatively coupledsuch that when one arm is driven by a motor the articulated arms extendand retract in a "froglike" or "frogkick" type of motion. A platform iscoupled to the arms and has the object to be transferred disposedthereon.

U.S. Pat. No. 4,951,601 discloses wafer transfer handling apparatushaving an articulated arm assembly which includes a dual four-bar linkpivot mechanism. However, such mechanism is subject to certain arbitrarymovement of the platform.

SUMMARY OF THE INVENTION

The present invention provides a simple and reliable device fortransferring objects, such as silicon wafers, camera lenses, crystaloscillators, or the like, between a plurality of locations disposed invarious axial and radial planes. This apparatus includes a dual four-barlink pivot mechanism having an improved link which prevents arbitrarymovement of the platform. The link includes two shafts which are coupledso that one shaft rotates in the sense which is opposite to the sense ofrotation of the other shaft.

The articulated arm assembly is preferably coupled to a base via arotation motor such that the entire articulated arm assembly may berotated in a radial plane. Like the apparatus of the prior art, suchrotation is done when the end effector is not in an extended position.

The articulated arm assembly is also, in one embodiment, preferablycoupled to the base via a plurality of flexures or levers that areresponsive to a force such that the platform assembly may be displacedin an axial direction. In another embodiment, the arm assembly ismounted, by means other than flexures, for axial movement through a muchlarger range than that attainable with flexures. The assembly isadaptable for use in a variety of environments, including operation in avacuum chamber or other controlled environment. The assembly may bemounted for movement inside a vacuum chamber with a vacuum seal betweenthe assembly and its support.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of an articulated arm assembly in accordance withthe present invention in a left-extended position;

FIG. 2 is a side view (partly in a section) of the apparatus shown inFIG. 1;

FIG. 3 is a top view of one form of link means for the apparatus ofFIGS. 1 and 2;

FIG. 4 is a side view of another form of link means for the apparatus ofFIGS. 1 and 2;

FIG. 5 is a section along the line 5--5 of FIG. 4;

FIG. 6 is a section along the line 6--6 of FIG. 4;

FIG. 7A is a sketch showing a first step in the assembly of the linkmeans of FIGS. 4 through 6;

FIG. 7B is a sketch showing the link means of FIG. 7A from a differentangle;

FIG. 8A is a sketch showing a second step in the assembly of the linkmeans of FIGS. 4 through 6;

FIG. 8B is a sketch showing the link means of FIG. 8A from a differentangle;

FIG. 9A is a sketch showing a third step in the assembly of the linkmeans of FIGS. 4 through 6;

FIG. 9B is a sketch showing the link means of FIG. 9A from a differentangle;

FIG. 10A is a sketch showing a fourth step in the assembly of the linkmeans of FIGS. 4 through 6;

FIG. 10B is a sketch showing the link means of FIG. 10A from a differentangle;

FIGS. 11A, 11B, 12A, 12B, 13A, and 13B are sketches showing the elbowband positions in the link means of FIGS. 4 through 6 during operationof the articulated arm assembly of FIGS. 1 and 2. FIG. 11A shows theupper arms at mid travel, FIG. 11B shows the forearms at mid travel,FIG. 12A shows the upper arms at full extend "A", FIG. 12B shows theforearms at full extend "A", FIG. 13A shows the upper arms at fullextend "B" and FIG. 13B shows the forearms at full extend "B"; and

FIG. 14 is a sketch showing the band and band end mounts used in thelink means of FIGS. 4 through 6.

FIG. 15 is a sketch of the link means for the apparatus in FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

The apparatus of the invention comprehends a four-arm lever connectionwhich has been referred to as a sidewinder arm assembly.

Referring to the drawing, the four arms include an upper slave arm 1, anupper drive arm 2, a lower drive arm 3 and a lower slave arm 4. Thesefour arms are supported upon various axles and shafts, as follows. Afirst end of the upper drive-arm 2 is fixed to a drive axle 6, so thatrotation of the drive axle 6 will rotate the upper drive-arm 2. A firstend of the upper slave arm 1 is rotatably mounted on a passive axle 5which permits the upper slave arm 1 to rotate freely, either because thepassive axle 5 is rotatably mounted in its socket or because the upperslave arm 1 is rotatably mounted on the passive axle 5.

A first end of the lower drive arm 3 is rotatably mounted on a passiveaxle 7, and a first end of the lower slave arm 4 is rotatably mounted ona passive axle 8. The passive axles 7 and 8 are mounted on an endeffector 9 in such a way that the straight line through the passiveaxles 7 and 8 is parallel to the straight line through the axles 5 and6. Free rotation-of the lower drive arm and the lower slave arm withrespect to the end effector 9 is permitted, either because the passiveaxles 7 and 8 are rotatably mounted on the end effector 9 or because thelower arms are rotatably mounted on their respective passive axles.

The second ends of each of the four arms are mounted on a link 10 in thefollowing manner. An upper shaft 11 and a lower shaft 12 are rotatablysupported on the link 10. The second end of the upper drive-arm is fixedto the upper shaft 11, and the second end of the upper slave arm rotateson the lower shaft. As a result, when either one of the upper armsrotates in one sense (e.g. counter-clockwise), the essentiallyparallelogram configuration of the two upper arms causes the other upperarm to follow the rotational movement of the said one upper arm. In theembodiment of FIGS. 1 and 2 the upper drive-arm 2 is fixed to the driveaxle 6, which is rotated by a suitable mechanism such as a gear drivenby a toothed shaft of a motor. However, it is also possible to rotatethe axle 5 by such a mechanism, the upper slave arm 1 being then fixedto the axle 5 while the upper drive-arm 2 is rotatably mounted on theaxle 6; in that event, the upper arm 1 would be designated the "drive"arm and the upper arm 2 would be designated the "slave" arm. In otherwords, the term "drive" arm refers to an arm which is fixed to a shaftand thus participates in the connective action of the link 10, to bedescribed hereinafter. The construction is such that the line joiningthe shafts remains parallel to the line joining the axles as rotationproceeds. The rotation of the upper drive arm in one sense (e.g.counter-clockwise) causes a similar rotation (counter-clockwise) aboutits own axis of the upper shaft, to which the upper drive arm is fixed.

The two shafts are connected by a connection which causes the lowershaft to rotate in a sense (e.g. clockwise) opposite to the sense ofrotation of the upper shaft. In one embodiment of the invention thisconnection comprises the combination of a toothed wheel fixed to theupper shaft which meshes with a toothed wheel fixed to the lower shaftin a gear connection, as shown in FIG. 3. In another embodiment of theinvention the two shafts are connected by two or more S-bands and wheelswhich are affixed to each of the shafts in the manner shown in FIGS. 4,5 and 6. Two S-bands are required, one for each sense of rotation of theupper shaft, because the transfer of rotation to the lower shaftrequires the action of an S-band in tension. Suitable materials for theS-bands include any spring alloy, i.e., any alloy for making springs. Apreferred material is a spring steel alloy, and the most preferredmaterial is the well-known alloy designated "ELGILOY", which is capableof being welded to other materials without cracking or warping. ELGILOYis a cobalt-nickel-iron alloy somewhat similar to the alloy known as "INCONEL".

The second end of the lower drive arm is fixed to the lower shaft, sothat the lower drive arm is rotated (e.g. clockwise) as the lower shaftrotates. The second end of the lower slave arm is rotatably mounted onthe upper shaft. The construction is such that the line joining theshafts remains parallel to the line joining the axles as rotationproceeds, and the essentially parallelogram configuration of the twolower arms causes the lower slave arm to rotate in synchronism with thelower drive arm.

As a result of the gear connection or S-band connection between theshafts, as the arms rotate the end effector is moved along the straightline through the passive axles 7,8. If all four arms have the sameaxle-to-shaft length, the end effector is moved along a line which runsthrough all four axles. If the length of the lower arms differs fromthat of the upper arms, the end effector is moved along a curved linebut remains parallel to the line between the axles 5, 6.

The assembly of the link means of FIGS. 4 through 6 is shown in FIGS.7A, 7B, 8A, 8B, 9A, 9B, 10A and 10B. Referring thereto, a first stepcomprehends the affixing of the upper drive arm 2 to the upper shaft 11and the affixing of the lower drive arm 3 to the lower shaft 12. (Itshould be noted that the view in FIG. 7A is that seen when the apparatusof FIGS. 1 and 2 is rotated about a horizontal axis 180 degrees, so thatthe upper drive arm 2 is above the upper slave arm 1 in FIG. 7A.) Asecond step is shown in FIGS. 8A and 8B and comprehends the placement ofthe link 10 upon the shafts 11 and 12. The link 10 is provided withbearings so that the shafts 11 and 12 may rotate with respect to thelink 10. A third step is shown in FIGS. 9A and 9B and comprehends theplacement of a lower drum 15 on the lower shaft 12 and the placement ofan upper drum 16 on the upper shaft 11. The term "upper" refers to theshaft or drum which is nearest the shoulder axles 5 and 6, at least oneof which provides the motive power, and the term "lower" refers to theshaft or drum which is the more remote from said shoulder axles 5 and 6and nearer to the end effector 9. The lower drum 15 is affixed to thelower shaft 12, and the upper drum 16 is affixed to the upper shaft 11.Each drum is adjacent the end of a drive arm to which it is connected bya suitable band affixed at one end to the drum and at the other end tothe drive arm. Extensions of each shaft are provided for the slave armbearings. The band 14 which connects the lower drum to the upper drivearm may be designated a "clockwise" band, since clockwise rotation ofthe upper drive arm 2 places this band 14 in tension so as to rotate thelower drum 15 counterclockwise. The band 13 which connects the upperdrum to the lower drive arm 3 may be designated a "counterclockwise"band, since counterclockwise rotation of the upper drive arm 2 placesthis band 13 in tension so as to rotate the lower drive arm 3 clockwise.Preferably the bands are always under some tension, since compressionforces within the band are undesirable.

FIGS. 7-10 show only the drive arms, in order to clarify the descriptionof the assembly of the link mechanism. The movement of the arms is shownin FIGS. 11-13, wherein FIGS. 11A, 12A and 13A each show the upper drivearm 2, the upper slave arm 1 and the lower drum 15 which, like the lowerdrive arm 3, is affixed or pinned to the lower shaft 12. The rotation ofthe drum 15 as between FIGS. 11A, 12A and 13A may be seen from theposition of the band end mount thereon. FIGS. 11B, 12B and 13B each showthe lower drive arm 3, the lower slave arm 4 and the upper drum 16which, like the upper drive arm 2, is affixed or pinned to the uppershaft 11. The rotation of the drum 16 as between FIGS. 11B, 12B and 13Bmay be seen from the position of the band end mount thereon. Thus, FIGS.11-13 show, not only the positions of the slave arms as well as thedrive arms, but also the coaction of each band with one drum and onedrive arm. The positions of the arms in FIGS. 12A and 12B correspond tothe positions of these arms in FIG. 1, rather than the "inverse" view ofFIGS. 7-10. As the end effector 9 of FIG. 1 is moved from the left sideof the drawing to the right side of the drawing, the arms movesequentially through the positions shown in FIGS. 11A and 11B (midtravel) and the positions shown in FIGS. 13A and 13B.

Each band conveys the rotary motion of a drive arm or a drum to a drumor a drive arm, respectively. The link 10 causes each slave arm tofollow the rotation of the corresponding drive arm about either theshoulder axles or the wrist axles, but any rotation of the shafts withrespect to the slave arms is unrestricted, as a result of the bearingsby which the slave arms are mounted on the extensions of the pivots.

As shown in FIG. 14, each end of each band is welded to a band endmount, which is then affixed to a drum or a drive arm by suitable pins,screws, or the like. During operation, the band which is underoperational tension exerts tension upon the weld, which it iswell-suited to sustain, and the band which is not under operationaltension is preferably under at least some minimal tension, sincecompressive forces at the weld or within the band are to be avoided.Such minimal tension may be provided when each band end mount is affixedto its drum and drive arm.

It will be noticed from FIGS. 7-10 that each drive arm cooperates (witha drum) in transferring the rotation of one shaft to the rotation (inthe opposite sense) of the other shaft. Therefore, as appears from FIGS.7B, 8B, 9B and 10B, there are five levels of components supported oneach shaft: namely, the upper slave arm 1 at a first level, the lowerdrum 15 and the upper drive arm 2 at a second level, the link 10 at athird level, the lower drive arm 3 and the upper drum 16 at a fourthlevel, and the lower slave arm 4 at a fifth level. Also, since eachdrive arm cooperates with a drum, the slave arm which is paired with adrive arm must be displaced to a level different from that occupied bythe drive-arm/drum combination. When the gear mechanism of FIG. 3 isemployed instead of the band/drum mechanism of FIGS. 4-6, each slave armmay occupy the same level as the drive arm with which it is paired, andthe two gear wheels may occupy their own, separate level. This resultsin part from the fact that when the gear mechanism of FIG. 3 isemployed, a single pair of gears can cause rotation in either sense.Therefore, as appears from FIG. 15, there are four levels of componentssupported on each shaft: namely, the upper drive arm 2 and upper slavearm 1 at a first level, the link 10 at a second level, the gears at athird level, and the lower drive arm 3 and lower slave arm 4 at a fourthlevel.

When the band/drum mechanism of FIGS. 4-6 is employed, one band/drumcombination must be used for each sense of rotation, because each bandcan usefully operate only in tension. In order to reduce the number oflevels required, it is convenient to affix one end of each band to the"elbow" end of a drive arm, rather than to another drum. When the gearmechanism of FIG. 3 is employed, it is not useful to form the elbow endof a drive arm as a gear wheel, because a greater saving of space isachieved by alloting separate gear wheels to their own level.

The essence of the link means is that each drive arm is affixed to ashaft, and a connection is provided which causes rotation of one shaftin one sense to cause rotation of the other shaft in the opposite sense.

Having thus described the principles of the invention, together withillustrative embodiments thereof, it is to be understood that althoughspecific terms are employed, they are used in a generic and descriptivesense and not for purposes of limitation, the scope of the inventionbeing set forth in the following claims.

We claim:
 1. An apparatus for transferring objects, comprising:asupport; a first upper arm supported on said support so as to berotatable about a first axis; a second upper arm supported on saidsupport so as to be rotatable about a second axis; a pair of forearms,comprising a first forearm and a second forearm, said pair of forearmsbeing articulated to said first and second upper arms by means of linkmeans; said link means comprising a link, an upper shaft rotatablysupported on said link and having a drum fixed thereto, and a lowershaft rotatably supported on said link and having a drum fixed thereto;said first upper arm being fixed to said upper shaft; said second upperarm being rotatably mounted on said lower shaft; said first forearmbeing fixed to said lower shaft; said second forearm being rotatablymounted on said upper shaft; crossed S-bands of which one extendsbetween said drum on said upper shaft and said first forearm and ofwhich the other extends between said drum on said lower shaft and saidfirst upper arm; holding means pivotally coupled to said pair offorearms; and means for driving at least one of said upper arms forrotation through an angle in the range of from greater than 120° up toand including 180° to move said holding means between an extendedposition and a retracted position.
 2. Apparatus for transporting anarticle, comprising in combination:a support; a first shoulder pivotsupported on said support and defining an axis of rotation, a secondshoulder pivot substantially parallel to said first shoulder pivot andsupported on said support and together with said first shoulder pivotdefining a first straight line passing through said first and secondshoulder pivots extending across said support, a first upper armrotatably mounted on said first shoulder pivot and having first elbowjoint means comprising at least one first elbow pivot fixed to saidfirst upper arm and spaced from said first shoulder pivot by said firstupper-arm length, said first elbow pivot having a first drum fixedthereto, a second upper arm rotatably mounted on said second shoulderpivot and having second elbow joint means comprising at least one secondelbow pivot rotatably connected to said second upper arm and spaced fromsaid second shoulder pivot by said second upper-arm length, said secondelbow pivot having a second drum fixed thereto, a first forearm fixed tosaid second elbow pivot and having a first wrist pivot spaced from saidsecond elbow pivot by said first forearm length, a second forearmrotatably mounted on said first elbow pivot and having a second wristpivot spaced from said first elbow pivot by said second forearm length,said second wrist pivot together with said first wrist pivot defining asecond straight line passing through said first and second wrist pivotsand parallel to said first straight line, a holding means mounted onsaid wrist pivots, link means connecting said elbow pivots, crossedS-bands of which one extends between said first drum and said firstforearm and of which the other extends between said second drum and saidfirst upper arm, and means for driving at least one of said upper armsfor rotation through an angle in the range of from greater than 120° upto and including 180° to move said holding means between an extendedposition and a retracted position.
 3. An assembly comprising: (a) an endeffector, (b) a pair of upper arms each having a shoulder end and anelbow end, (c) a pair of forearms each having a wrist end and an elbowend, and (d) a support,the elbow ends of said upper arms being connectedto the elbow ends of said forearms by link means, the wrist ends of saidforearms being mounted to the end effector and the shoulder ends of saidupper arms being mounted to the support, said link means including afirst shaft having a first drum fixed thereto and rotatably connected tothe elbow end of one forearm and fixed to the elbow end of one upperarm, said link means including a second shaft having a second drum fixedthereto and rotatably connected to the elbow end of the other upper armand fixed to the elbow end of the other forearm, crossed S-bands ofwhich one extends between said first drum and the elbow end of theforearm to which said second shaft is fixed and of which the otherextends between said second drum and the elbow end of the upper arm towhich said first shaft is fixed; and means for imparting R and θmovement to the end effector via the upper arms and forearms.
 4. Anapparatus for transferring objects, comprising:a support having a firstaxle and a second axle adjacent to said first axle; a first upper armhaving a shoulder end and an elbow end, said shoulder end beingrotatably supported on said first axle; a second upper arm having ashoulder end and an elbow end, said shoulder end being rotatablysupported on said second axle; an end effector having a first axle and asecond axle adjacent to said first axle; a first forearm having a wristend and an elbow end, said wrist end being rotatably attached to saidfirst axle of said end effector; a second forearm having a wrist end andan elbow end, said wrist end being rotatably attached to said secondaxle of said end effector; link means, said link means comprising (1) alink having a first aperture, a second aperture adjacent to said firstaperture, a first side and a second side, (2) an upper shaft having afirst drum fixed thereto and rotatably supported within said firstaperture, and (3) a lower shaft having a second drum fixed thereto androtatably supported within said second aperture; said elbow end of saidfirst upper arm being fixed to said upper shaft on said first side ofsaid link; said elbow end of said first forearm being fixed to saidlower shaft on said second side of said link; said elbow end of saidsecond upper arm being rotatably mounted on said lower shaft on saidfirst side of said link; said elbow end of said second forearm beingrotatably mounted on said upper shaft on said second side of said link;crossed S-bands of which one extends between said first drum and saidelbow end of said first forearm and of which the other extends betweensaid second drum and said elbow end of said first upper arm; and meansfor driving at least one of said upper arms for rotation through anangle in the range of from greater than 120° up to and including 180° tomove said end effector between an extended position and a retractedposition.
 5. An apparatus in accordance with claim 1, wherein saidS-bands consist essentially of a spring steel alloy.
 6. An apparatus inaccordance with claim 5, wherein said spring steel alloy is acobalt-nickel-iron alloy.
 7. Apparatus in accordance with claim 1,wherein said means for driving at least one of said upper arms drivessaid first upper arm.
 8. Apparatus in accordance with claim 2, whereinsaid means for driving at least one of said upper arms drives said firstupper arm.
 9. Apparatus in accordance with claim 3, wherein said meansfor imparting R and θ movement includes means for driving the upper armthe elbow end of which is fixed to said first shaft.
 10. Apparatus inaccordance with claim 4, wherein said means for driving at least one ofsaid upper arms drives said first upper arm.